Comparison of sorbents and isotherm models for NH<sub>3</sub>‐gas separation by adsorption

Helminen, Jarkko; Helenius, Joni; Paatero, Erkki; Турунен, Илкка

doi:10.1002/aic.690460807

Cited by 70 publications

(60 citation statements)

References 27 publications

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“…The parameters used in this work were therefore inspired by parameters from the literature, but primarily obtained by trial and error, fitting them to the available experimental isotherms. Figure 5 shows the adsorption isotherms for NH 3 on zeolite 4A at different temperatures and their comparison with experimental results obtained by Helminen et al [10][11] The errors in the simulations are approximately 10% of the calculated values, and are not shown in the figures. The agreement between the experimental and simulated isotherms is very good and it is remarkable that it extends over five orders of magnitude in pressure and 100 K in temperature.…”

Section: Methodsmentioning

confidence: 95%

Modeling local chemistry in the presence of collective phenomena.

Chandross¹,

Modine²

2005

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Confinement within the nanoscale pores of a zeolite strongly modifies the behavior of small molecules. Typical of many such interesting and important problems, realistic modeling of this phenomena requires simultaneously capturing the detailed behavior of chemical bonds and the possibility of collective dynamics occurring in a complex unit cell (672 atoms in the case of Zeolite-4A). Classical simulations alone cannot reliably model the breaking and formation of chemical bonds, while quantum methods alone are incapable of treating the extended length and time scales characteristic of complex dynamics. We have developed a robust and efficient model in which a small region treated with the Kohn-Sham density functional theory is embedded within a larger system represented with classical potentials. This model has been applied in concert with first-principles electronic structure calculations and classical molecular dynamics and Monte Carlo simulations to study the behavior of water, ammonia, the hydroxide ion, and the ammonium ion in Zeolite-4a. Understanding this behavior is important to the predictive modeling of the aging of Zeolite-based desiccants. In particular, we have studied the absorption of these molecules, interactions between water and the ammonium ion, and reactions between the hydroxide ion and the zeolite cage. We have shown that interactions with the extended Zeolite cage strongly modifies these local chemical phenomena, and thereby we have proven out hypothesis that capturing both local chemistry and collective phenomena is essential to realistic modeling of this system. Based on our results, we have been able to identify two possible mechanisms for the aging of Zeolite-based desiccants.-3 - CONTENTS

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Section: Methodsmentioning

confidence: 95%

Modeling local chemistry in the presence of collective phenomena.

Chandross¹,

Modine²

2005

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“…As must be clear from above, the inference-based approach may lead to a set of statistically valid models. In the Bayesian approach actually no choice is made, although a user might define a probability level as a lower bound for [13] a valid model. Similarly, the optimization-based selection could use a deviation from the global optimum in order to define a finite set of models.…”

Section: Discussionmentioning

confidence: 99%

“…An extensive example of the application scheme in Figure 1 is given through a study of isotherm models for the adsorption of ammonia by Helminen et al [13]. They considered 16 different isotherm models and three different 5 different sorbents.…”

Section: Ammoniamentioning

confidence: 99%

Model selection: An overview of practices in chemical engineering

Verheijen

2003

Computer Aided Chemical Engineering

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The problem of choosing out of a large set of models is considered here. Five criteria are mentioned: the level of rigor that a model describes phenomena; the accuracy of the model with respect to data; the adequacy of the model for the purpose of simulation, optimization or design; the flexibility of a model; and the computational complexity. The focus is on the purely statistical criteria. A systematic procedure is presented to eliminate sequentially hierarchical models and equivalent models, based on the F-test and Bartlett's χ 2 -test. The use of Bayesian statistics as a tool is reviewed. And recent developments in optimization-based approaches are listed. An overview of available measures for the distance between models is given. It is shown that one should not accept a single model, as is engineering practice, but rather allow for a set of models when the selection does not give sufficient reason to discriminate between models. Examples from the area of reaction kinetics and adsorption are given.

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“…Experimental data were fitted to Langmuir and Freundlich isotherm models, since they are the most common patterns used for predicting adsorption performance in biofiltration (Delhoménie et al, 2002;Helminen et al, 2000). A summary of the results of the adsorption isotherms is shown in Table II.…”

Section: Adsorption Of Ammonia On Organic Materialsmentioning

confidence: 99%

“…These phenomena are believe to play a key role in the performance of biofilters, especially under transient conditions or shock loading, since absorption and adsorption may act as buffer for biological activity (Barona et al, 2005;Mcnevin and Barford, 2001). To our knowledge, only few studies have been focused on the adsorption of some pollutants in compost or peat (Delhoménie et al, 2002;Mcnevin and Barford, 1998), being the absorption and the combined adsorption-absorption studies very scarce and usually conducted on synthetic or well-defined inorganic materials (Helminen et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

Adsorption, absorption, and biological degradation of ammonia in different biofilter organic media

Pagans

Font

Sánchez

2006

Biotech & Bioengineering

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A tailor-made apparatus called ammoniometer, which is a batch mode respirometer applied to the study of ammonia biodegradation in biofilter media, has been used to evaluate adsorption, absorption, and biodegradation in five different organic materials (compost, coconut fibre, bark, pruning wastes, and peat) obtained from full-scale biofilters in operation in several waste treatment plants. The results showed that absorption could be represented by a Henry's law linear equation, with values of the Henry coefficient significantly higher (from 1,866 to 15,320) than that of pure water (1,498). Adsorption data were successfully fitted to Langmuir and Freundlich isotherms and maximum adsorption capacity varies from 1.06 to 1.81 mg NH(3)/g dry media. Ammonia biodegradation rates for each organic material were also calculated. Biodegradation rates varied from 0.67 to 7.82 mg NH(3)/kg media/d depending on the material tested. The data obtained showed important differences in the behaviour of the biofilter organic media, which has important implications in the design and modelling of these systems.

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Comparison of sorbents and isotherm models for NH₃‐gas separation by adsorption

Abstract: Adsorption equilibrium isotherms of ammonia gas were measured at temperatures between 298 and 393 K on 13X zeolite, 4A zeolite, alumina, silica gel, and

Cited by 70 publications

References 27 publications

Modeling local chemistry in the presence of collective phenomena.

Modeling local chemistry in the presence of collective phenomena.

Model selection: An overview of practices in chemical engineering

Adsorption, absorption, and biological degradation of ammonia in different biofilter organic media

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Comparison of sorbents and isotherm models for NH3‐gas separation by adsorption

Abstract: Adsorption equilibrium isotherms of ammonia gas were measured at temperatures between 298 and 393 K on 13X zeolite, 4A zeolite, alumina, silica gel, and

Cited by 70 publications

References 27 publications

Modeling local chemistry in the presence of collective phenomena.

Modeling local chemistry in the presence of collective phenomena.

Model selection: An overview of practices in chemical engineering

Adsorption, absorption, and biological degradation of ammonia in different biofilter organic media

Contact Info

Product

Resources

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Comparison of sorbents and isotherm models for NH₃‐gas separation by adsorption